Etymology

Like many other members of the House of Black, Cygnus is named after a constellation. Cygnus is a northern constellation known as the Swan or the Northern Cross. It was named for several swans which appear in Greek mythology, including the one Zeus transformed into to seduce Leda, the form Orpheus took after his death, and a son of the god Apollo who was turned into a swan after his murder. The name is derived from the Greek κύκνος, kyknos, meaning "swan".

Behind the scenes

Cygnus and his wife were likely in Slytherin house like the rest of the family.

↑Bellatrix says in Deathly Hallows: "We – Narcissa and I – have never set eyes on our sister since she married the Mudblood." This suggests that the family as a whole refused to see Andromeda after her marriage and disownment.